Her mother, Rita, was also obese and followed her daughter's progress carefully. After witnessing Caitlin's dramatic weight loss, she decided to follow in her daughter's footsteps and had her own surgery done in April, although it was a different procedure.

"She saw how much weight I lost and how happy it made me, and she said she wants to me like me," Dunnings said. "She's already lost about 80 pounds."

Study: Surgery Leads to Healthier Lifestyles for Family, Too

But the impact of the women's surgery goes beyond their weight loss and personal satisfaction. Dunnings said their success motivated her father and brother to start eating right and thinking about their own waistlines, albeit without surgical intervention.

A new study published in Archives of Surgery suggests the Dunnings men are not the only ones to reap benefits from family members who undergo weight-loss surgery.

"We found that after surgery, patients lost a lot of weight, but obese adult family members lost a significant amount of weight as well and so did kids," said Dr. John Morton, a study co-author and director of minimally invasive and bariatric surgery at Stanford University Medical Center in Palo Alto, Calif.

Morton and his colleagues followed 35 families of patients who had a specific gastric bypass procedure for one year. The patients and their families attended counseling sessions before and after surgery that taught them about the importance of adopting healthier eating habits and getting more physically active.

In addition to weight loss, adults reported better eating habits and less alcohol consumption, and children spent less time in front of a television or a computer and more said they were on a diet.

"Part of it had to do with the education they received through counseling," said Morton.

"When they come in and listen, they learn what obesity is and that a lot of their medical problems are related to their weight, which has a big impact," said Dr. Nestor de la Cruz-Munoz, chief of laparoendoscopic and bariatric Surgery at the University of Miami's Miller School of Medicine. He had no involvement with the new research.

Morton said that another big component was that the majority of patients in the study were women. Women often make the household decisions about what kind of food to buy and how to cook it.

"Often, I hear, especially from mothers, that they want bariatric surgery so that they can make the healthy choices for their families and help their children avoid the patient's own struggles with obesity," said Dr. Peter Liao, diirector of the Comprehensive Obesity Management Program at Greater Baltimore Medical Center in Baltimore. Liao was also not involved in the study.